A variety of radio systems are available nowadays for transmitting signals wirelessly over a very short distance of less than approximately 1.5 m. Examples of such systems are Bluetooth, NFC (Near Field Communication) and WLAN (Wireless Local Area Network), etc. In general, all radio systems suffer from one common problem, namely how to obtain as wide as possible a radio range at the lowest possible power consumption. If the distance between sender and receiver is too great or if the radio power is too low, errors in the data transmission may occur, possibly even resulting in a complete breakdown of a radio link.
Various methods have been devised to increase the radio range of a transmitter/receiver system. One is published in EP 1 026 779 A2, which discloses a dipole antenna with a loop as a first pole and an appendage with a strip terminating in a pad as a second pole. The circumference of the loop is of the order of one half-wavelength of an operation frequency and an effective length of the appendage is at least 0.15 times the wavelength. Since the loop of the antenna is of the order of one half-wavelength of an operation frequency, it generates an electromagnetic wave and the electric charge is not uniformly distributed over the loop. However, the use of such an antenna furthermore results in correspondingly bulky devices, in particular if the chosen frequency for the radio transmission is relatively low, since the antenna is then relatively large. The ever decreasing size of present-day devices, necessitates the choice of a relatively high frequency for the radio link, which obviously is a limitation in designing such a device, in particular because fewer free frequencies are available for radio links than was the case in earlier times.